Monday, May 11, 2015

Ubiquinone,
also known as coenzyme Q, coenzyme Q10, ubidecarenone, Q or Q10 is a
hydrophobic 1,4-benzoquinone that belongs to the class of isoprenoid compounds
(the number 10 in Q10 represents the number of isoprene units in its tail). It
was first discovered in 1957 and a year later its chemical structure was
described.

It has
antioxidant properties, that means, it has the ability to act in
oxidation-reduction reactions. In fact, its oxidized form may accept two
electrons, passing to the reduced form, ubiquinol (sometimes represented as
QH2). It may also be in an intermediate state (ubisemiquinone). This redox
ability makes it useful in eliminating free radicals, as well as in electron
transfer processes. And this is exactly its main function in our body: it is
one of the components of the mitochondrial respiratory chain. Although not being
part of any complex of the chain, it plays a key role in the process, because it
accepts electrons from the complex I or complex II and delivers them to complex
III. To exert this function, ubiquinone takes advantage of its high membrane diffusivity,
which allows it to diffuse easily across the mitochondrial inner membrane, a
consequence of its small size and hydrophobic character. Ubiquinone is present
in most eukaryotic cells, specifically in the inner mitochondrial membrane. Nevertheless,
it is also found in lesser amounts in the membrane of several other organelles
such as peroxisomes, endoplasmatic reticulum and lysosomes.

The
synthesis of ubiquinone shares several steps with the synthesis of cholesterol,
namely until the production of mevalonate. Globally, it is a complex process,
which uses at least 12 enzymes, and occurs in mitochondria, endoplasmic
reticulum and peroxisomes. The synthesis of ubiquinone involves the HMG-CoA
reductase enzyme, which is the main pharmacological target of statins (drugs
used in individuals with an excess of cholesterol in the body, through the
inhibition of the synthesis of the lipid). Consequently, one of the side
effects of its adminis of statins may be a decrease in ubiquinone production.